MIAMI (Reuters) — While Roger Federer and
Rafa Nadal may be the most trendy rivalry in men's tennis, the most
enduring may be top ranked Nadal and Novak Djokovic, who clashed for the
40th time on Sunday in the final of the Sony Open.

Any final featuring the world's two top-ranked players
automatically qualifies as significant but Nadal and Djokovic have
elevated their clashes to something special.

Despite Sunday's loss, Nadal continues to hold a slight edge, 22-18,
in their head-to-head meetings, 20 of the matches having come with a
title on the line, including six grand slam finals.

With Djokovic's Miami victory, he and Nadal between them now hold
all nine Masters series titles.

"Definitely the biggest rivalry I have in my tennis career," said
Djokovic without hesitation. "It's a great challenge always when I
play Rafa on any surface, of course, especially on clay.

"That is his most preferred surface, his most dominant there."

Their meetings in recent years have especially been ones to
remember, Djokovic said.

"I have had some thrilling matches in last three or four years, and
they were decided by few points," he said.

"Very few matches that were one-sided, so I knew what to expect from
Rafa today."

Four times Nadal has finished runner-up on the Miami hardcourts,
with Djokovic ending his title hopes twice.

Asked if he enjoyed the challenge of playing Djokovic and was happy
the two were playing in the same era, Nadal was quick to the point.

" No," said the Spaniard. "I like challenges but I am not stupid."

Djokovic, however, when asked the same question, delivered a
thoughtful answer.

"I think the challenges, big challenges that I had in my career
changed me in a positive way as a player," said Djokovic. "Because
of Rafa and because of Roger I am what I am today.

"All the big
matches I lost to these guys was consistent, but not winning the big
matches made me understand what I need to do on the court.

"You have to win against the best players in the world. That's
the biggest challenge you can have."

Over the years, taking on Nadal presented Djokovic with his biggest
and most enduring challenge, one he has met with continued
excitement despite losing more often than he has won.

"When he fights for trophy, he comes out with a great intensity from
the first point, and he wants to make sure he sends the message
across the net to his opponent," said Djokovic. "That rivalry that
we have is obviously great for the sport.